U.S. Pat. No. 3,614,966 marked an improvement in pilot operated evaporator pressure regulator valves but was subject to impaired performance under certain conditions. Orth et al. application Ser. No. 308,029, not U.S. Pat. No. 3,810,488, improved upon the patent structure but both are subject to freeze-up in systems containing excessive moisture (about 300 ppm). Thus they operate well in a "dry" type automotive air conditioning system since the system handles refrigerant above the freezing point of water. In a "flooded" type system, however, the refrigerant is close to 0.degree.C and water could freeze and cause malfunction of the valve.